SUMMERY (SUMMARY) OF ELECTRON CONFIGURATIONS 11 Na THERE ARE TWO ELECTRONS IN SHELL N=1 ( lowest energy level in Na) THE GROUND STATE CONFIGURATION: 1) Given on periodic table. 2) Inner shells are full ( except transition metals, where the last two shells may be incomplete). 3) Most stable, lowest energy configuration. 4) Lower shell numbers are closest to the nucleus and are lowest in energy level. 5) Electrons must exist in shells, also termed energy levels and principle quantum number. 6) The outer shell is the valence shell and is chemically reactive, inner shells are kernel electrons and are chemically inactive. THERE ARE EIGHT ELECTRONS IN SHELL N=2 THERE IS ONE ELECTRON IN SHELL N=3 VALENCE SHELL( highest energy level here)

THERE ARE TWO ELECTRONS IN SHELL N=1 THERE ARE EIGHT ELECTRONS IN SHELL N=2 THERE ARE TWO ELECTRON IN SHELL N=4 VALENCE SHELL 25 Mn THERE ARE 13 ELECTRONS IN SHELL N=3, TRANSITION METALS (GROUPS 3-12) FREQUENTLY HAVE THE OUTER TWO SHELLS INCOMPLETE. THIS BACKGROUND IS CORN-Y

THE EXCITED STATE CONFIGURATION: 1) Same number of electrons as ground state, different configuration. 2) An electron is promoted from an inner shell (lower energy) to an outer shell (higher energy). 3) An inner shell that is full in the ground state will be incomplete in the excited state. 4) The excited state is temporary and is imediatley followed by fallback. 11 Na GROUND STATE EXCITED STATE THIS INNER SHELL IS NOT FULL (SHOULD HAVE 8 ELECTRONS) WHICH IS INDICATIVE OF AN EXCITED STATE EXCITED STATE

nuc n=1 n=2 n=3 11 Na e- ENERGY EXCITATION e-

ELECTRON HOLE, THE VACATED FORMER POSITION OF THE ELECTRON, THE n=2 SHELL IS NO LONGER COMPLETE. nuc n=1 n=2 n=3 11 Na e- EXCITED STATE, THE ELECTRON IS IN A HIGHER ENERGY LEVEL THAN ITS GROUD STATE POSITION.

nuc n=1 n=2 n=3 11 Na e- FALLBACK DURING FALLBACK ENERGY IS RELEASED AS LIGHT DURING FALLBACK ENERGY IS RELEASED AS LIGHT DURING FALLBACK THE ELECTRON BECOMES MORE STABLE AS IT RELEASES ITS ENERGY, GOES BACK TO GROUND STATE. e-

nuc n=1 n=2 n=3 11 Na e-

INCREASING ENERGY

U DO IT NOW! For the following configuration: a) Identify the element. b) Propose an excited state. c) How many electrons are in the valence shell? Simply add the electrons, which equal protons in a neutral atom, the atomic number : = 34 electrons indicates an atomic number of 34, which is Se Write a configuration with the same number of electrons as the ground state, but with a different configuration (ground): (excited) ♫NOTE – electrons furthest from the nucleus are most likely to be excited (promoted) , 6 valence electrons (and = 26 kernel)